Beta 1 of Virtual Server 2005 R2 service pack 1 is available to download. General availability is expected in calendar Q1 2007.  Here’s a quick description from Microsoft Connect download site:

It provides improved reliability and performance across mixed workloads by leveraging hardware virtualization assists, high availability for both planned and unplanned downtime and improved support for backup and disaster recovery.

We’ll have two betas of Virtual Server 2005 R2 Sp1.  Beta 2 is scheduled for Q4 this year. Here’s how the features shape up for each beta.
Beta 1 of Virtual Server 2005 R2 service pack 1 includes:
  • Intel Virtualization Technology compatibility
  • Host Clustering technical white paper and the VB script
Beta 2 includes the features of Beta 1 plus:
  • AMD Virtualization compatibility
  • Active Directory integration and management features
  • Volume Shadow Service (VSS)
  • Expanded guest and host OS support
You might ask, “why doesn’t Beta 1 support AMD-V?”
Well, AMD Virtualization is tied to the release of the AMD Opteron socket 1207, which is said to be available in Q3 2006.  So availability of beta 2 of Virtual Server 2005 R2 Sp1 is dependent on the availability of socket 1207, and time for our internal testing.  It’s one of those ‘if we can get it out faster, we will.’
Another question we get on this topic is, Are VMs running in Virtual Server 2005 R2 Sp1 compatible between Intel VT/AMD-V hardware?”  The answer is yes. However, you must shutdown a VM before moving it. Saved states are not compatible.
For those not familiar with VSS, here’s a quick description:
provides users with improved support for backup and disaster recovery. Instead of backing up each virtual machine individually, users will be able to backup just physical machines that will in turn backup all the virtual machines on that physical host.